Luxman C7 & M7 Pre And Power Amplifier Made in Japan ( PL )

LUXMAN C-7

Control amplifier which adopted the perfect balance CSSC circuit.

C-7 employs a fully-complementary CSSC (Complimentary Single Stagger Circuit) circuit with a direct complementary configuration.
The CSSC circuit incorporates a base-grounded current transmission circuit in the second stage, and realizes natural signal amplification that does not require extra phase correction by taking a sufficiently high cutoff frequency. In C-7, this CSSC circuit has a perfect balance configuration, and the ground potential difference is completely eliminated to clarify the reference point. Thereby, while operating each amplifier on the same time axis, while eliminating a phase difference completely, the noise mixed in the signal was canceled mutually and the further sound quality improvement is realized.
Moreover, the discrete buffer amplifier of the complimentary composition with a very high-speed characteristic is adopted as the impedance conversion for ensuring the stability of an input signal, and the input impedance is taken high enough.

ODβ (Optimaized Dual NFB) circuit, which is a compilation of NFB technology accumulated by Lux for many years, is adopted.
In general amplifiers, the sound quality of the playback band is adjusted by NFB, with AC NFB affecting the mid-high range and DC NFB affecting the low-frequency sound quality. In this DC and AC feedback system, a DC servo amplifier is inserted to control the DC feedback, which has a large effect on the low range, resulting in inconsistencies in the timbre in the mid-high range and low range. .
The ODβ circuit adopted for C-7 refines the bare characteristics of the circuit and applies 100% DC feedback to ensure DC stability while eliminating DC servo amplifiers, making all bands a natural tone Are unified.

The original high inertia power supply is adopted as a power-source part.
In high inertia power supply, while improving regulation and adopting a custom electrolytic capacitor etc., instantaneous supply capability is improved, and the stability of the regulator circuit itself is secured by improving the bare characteristic. And by minimizing the excessive control delayed from the real time of music and performing only the minimum necessary control, the unnatural voltage fluctuation that fluctuates little by little is changed into a loose fluctuation, and power supply that brings natural sound quality to the sense of hearing Is possible.

Based on a five-point grounding type large mass FRP chassis base that excels in vibration absorption mode, a high-rigidity construction that suppresses unnecessary vibrations is realized by firmly fixing the parts to a thick hard chassis.
In addition, noise countermeasures are also thoroughly implemented, and in order to prevent the generation of flux and noise caused by the general arrangement of power transformers, chemical capacitors, and amplifiers next to each other, they are laid out so that they do not interfere directly with each other. At the same time, each block is blocked by a shield plate.
Furthermore, high frequency noise and leakage flux are eliminated by rationally subdividing each stage.

The independent power room method is adopted as a measure against leakage flux in the power supply.
In the external power supply method used as a countermeasure against leakage flux, the supply impedance increases, so the instantaneous supply capability is lost and the efficiency as a regulator power supply is reduced.
In C-7, the leakage flux is eliminated while putting the power supply part in the same case by the independent power supply room system which makes the power supply part such as transformer, rectifier diode, block capacitor, etc. completely separate from the signal path. Moreover, the influence from various vibration noises is intercepted by making the connection with a main part chassis semi-floating.
Furthermore, the constant voltage circuit is placed on the amplifier side to suppress the effects of control time delay and interference noise.

Custom parts are used everywhere to get a high level of sound quality.
C-7 uses non-magnetic high sound quality type large-sized carbon film resistors, electrolytic capacitors, copper styrol capacitors, etc., custom-made products of Lux specifications. In addition, a closed-type gold-plated contact relay is adopted for various switching functions, and the information transmission capability is improved by a relay that has been polished to expand the contact area.

The low distortion and low-noise 4-unit type level control corresponding to perfect balance is adopted as level control.
This volume has been newly developed by examining noise and phase problems caused by contacts from various angles.

Lux type NF type tone control all is adopted for tone control.

The input terminal is equipped with 5 coaxial lines and 2 balanced lines, and the output terminal is equipped with 2 coaxial lines and 2 balanced lines. Bi-amp drive can be connected in both balanced and unbalanced ways.
Two tape input / outputs are also installed.

The line phase sensor is carried and the polarity of a power supply can be checked at a glance.

A custom-made product that focuses on sound quality is used for the power cable.
This cable is an AC inlet type.

The remote terminal is carried and the power on / off of a power amplifier can be interlocked with C-7 by connecting with Lux power amplifier B-10, M-7, etc.

A 15mm thick aluminum panel is used for the front panel, and a glossy wooden cabinet is used for the cabinet.

There was a version upgrade service from C-7 to C-7i.

LUXMAN M-7 

Stereo power amplifier developed following the development concept of B-10.

CSSC (Complimentaly Single Stagger Circuit) circuit is adopted to reproduce the rising of sound more vividly.
The CSSC circuit consists of all stages directly connected complementary. The first rank serves as a complementary circuit of a dual FET differential and a cascode connection transistor. The second stage uses a grounded base type current transmission circuit, and the cut-off frequency is sufficiently high so that the amplifier bandwidth can be secured only by the first stage phase rotation, so a natural signal that does not require sufficient phase correction. Amplification is realized.
The current amplification stage is a three-stage Darlington complementary circuit with a high amplification factor, and the final stage has a push-pull configuration using six large-channel bipolar transistors (Pc150W) with one channel. , Ensuring excellent driving ability.

The original ODβ (Optimized Dual NFB) circuit is adopted in order to align the tone of all bands.
In general NFB, a system that uses separate feedback for direct current and alternating current is used. At this time, AC affects the sound quality of the mid-high range, and DC affects the sound quality of the low range, but in order to control the low range, a servo amplifier is inserted only in the DC range to give a large amount of NFB. This created a sense of inconsistency in the low and low frequency sounds.
In the ODβ circuit adopted in M-7, DC stability is secured while eliminating the DC servo amplifier by highly elaborating the nakedness characteristics of the circuit, and a natural sense of tone is obtained.

The original high inertia power supply is adopted as a power-source part.
The M-7 uses a toroidal power transformer with increased regulation, and has improved the bare characteristics such as increasing the instantaneous supply capability with a large-capacity block capacitor, so that small voltage fluctuations generated by music signals are relaxed. It has been changed to the fluctuations that have been achieved, and a natural power supply has been realized.

Not only can it be used as a stereo power amplifier, it can also be used as a high-power monaural power amplifier with BTL connection.

High rigidity construction is adopted to reduce unnecessary vibration and noise.
The M-7 uses a 5-point grounding type high-mass FRP chassis base that excels in vibration absorption mode, and maintains a weight balance by using a symmetrical structure. In addition to taking care not to cause a temperature difference in the housing, measures are taken for the material, layout, and shape, such as setting a unique shape to suppress the noise of the heat sink.
In addition, as a countermeasure against noise, a box blocking structure is adopted. In order to eliminate mutual interference between each circuit, each circuit is blocked by a shield plate, and each stage is rationally subdivided to further reduce high-frequency noise. And the flux is cut off.

Power supply parts, such as a transformer, a rectifier diode, and a block capacitor, are the independent power supply room system of the bulkhead structure completely separated from the signal path, and are suppressing the influence of various interference noise and unnecessary vibration.
Furthermore, the constant voltage circuit is laid out on the amplifier side, eliminating the effects of control time delay and interference noise.

The L / R independent attenuator which adopted the 6 contact independent fixed resistance switching system as a level control mechanism is adopted. By making it an attenuator type, stray current inside the printed resistor seen with slide type resistors does not occur, and sound quality degradation is reduced.
With this attenuator, you can select 6 positions: -∞, -30dB, -20dB, -12dB, -6dB, 0.

The input terminal is equipped with two lines, a balance terminal and an RCA terminal. Moreover, the output terminal is equipped with the original speaker terminal corresponding to an original development banana terminal and Y lug, and the speed controller terminal used in the sound field is also installed.

Custom parts, such as non-magnetic resistors, electrolytic capacitors, and copper styrene capacitors, are also used for B-10.
Furthermore, the fluctuation of impedance is suppressed by using a copper bus bar.

Lux's original line phase sensor is installed, and the polarity of the system can be unified.

The remote control terminal is carried and the power on / off can be interlocked when the control amplifier with the remote control output is connected.

A custom-made dedicated cable is used for the power cable.
Moreover, the AC inlet type is adopted as a power connector.

A large power display meter of 120x100mm is adopted as a power meter.
This meter has an illumination effect that projects the brand logo in three dimensions.

The aluminum panel and the wooden cabinet which gave original surface processing are adopted.

There was a version upgrade service to M-7i (improved model).